The use of getter materials for removing residual gas molecules from a vacuum and for purification of gases from active gas impurities is well known. These materials can, for example, absorb or react with the residual gases and gas impurities when they are placed inside a vacuum device.
There are applications of getter materials, where they have to show maximum high sorption capacity at room or close to room temperature. Such can, for example, be the case of sealed-off chambers in micro- or optoelectronics, portable analytical devices, e.g., gas chromatography-mass spectrometry (GC-MS) detectors, gas purifiers used in the production of high purity gases, etc.
It is known that transitional metals, which are the basis of commonly used getters, can capture most active gases at room temperature only by adsorption. Accordingly, their effectiveness or, in other words, their relative sorption capacity Cr, (which is proportional to the value r−1, where r is a typical size of a getter body, e.g., the radius of a continuous particle, the thickness of continuous film, etc.) is extremely small, which creates significant difficulties, when such getter materials are used.
On the other hand, many different alloys of barium and/or lithium with stable in the air metals, belong to substances, which can sorb oxygen, nitrogen and other gases with the sufficient for practical needs rate without heating. In contrast to transition metals, such barium and/or lithium alloys can react with gases to completion, (i.e., Cr˜1), thereby forming a layer of products on the surface of the getter material. Such a layer can further grow in accordance with the diffusional kinetics. However, the employment scale of barium and lithium in getter technologies is hitherto very limited.
For example, U.S. Pat. Nos. 5,312,606 and 5,312,607 to Boffito and Schiabel describe the processes for the sorption of residual gas in a vessel by means of a non-activated, non-evaporated barium getter. These processes comprise the steps of reducing alloys of barium as well as barium and lithium to a particle size of less than 5 mm, under vacuum or an inert gas atmosphere and then placing the particulate alloy in the vessel. Upon exposing the particulate alloy to the residual gas in the vessel at room temperature the gas is sorbed.
It should be understood that the material described in U.S. Pat. Nos. 5,312,606 and 5,312,607 has a continuous cast structure and widespread in the particle size distribution. Accordingly, such a material is not able to provide reproducibility and stability of the sorption process over time.
U.S. Pat. Appl. Pub. No. 2006/0225817 to Chuntonov describes a method for obtaining of skeleton-type granules of an alloy AnMem with high concentration of alkaline-earth metal A by evaporation of its excess from cast shot under vacuum.
International Patent Appl. WO2009/053969 to Chuntonov describes a lithium based getter material with high surface area. The material is manufactured in the form of granules of 0.2 mm to 2.5 mm in diameter with the structure of a dendritic carcass. This material has a relatively high sorption capacity and resistance to chemical shocks.
It should be noted that although the getter materials described in US2006/0225817 and WO2009/053969 provide a relatively constant sorption rate over almost the entire operating time of the material, the technology of dispersion of chemically active melts containing a volatile component is quite complex and requires special skills and knowledge from an operator.